A class mixes red and blue paint in the ratio 4 : 7 to make purple. They need 33 litres of purple paint. How many litres of blue paint must they use? If they decide instead to add 2 litres more red paint but keep the blue the same, what will the new ratio of red to blue be?
(a)How many litres of blue paint are used?(3)
(b)If 2 litres more red are added but blue remains the same, what is the new ratio of red to blue? Give the ratio in its simplest whole-number form.(3)